Hamman\'s syndrome - pneumomediastinum, subcutaneous emphysema and pneumorachis

Clinical History

A 24 year-old female came to the emergency department complaining of increased dyspnoea over the last hours. She also reported cough and thoracic pain. On arrival the patient had tachycardia, tachypnea. The patient was previously healthy and denied any trauma or drug abuse.

Imaging Findings

The chest radiograph (Figure 1) revealed the presence of free air in the supra-clavicular soft tissues, consistent with subcutaneous emphysema. Air could also be identified outlining the mediastinal pleura, along with the continuous diaphragm sign, confirming the presence of pneumomediastinum.
The non-contrast-enhanced CT (Figure 2) demonstrated subcutaneous emphysema, pneumomediastinum, as well as the presence of air in the cervical canal, consistent with pneumorachis. The track of air contacting the cervical deep soft tisses to the vertebral canal can be seen through the conjugated foramen.

Discussion

Pneumomediastinum is a condition defined by the presence of air in the mediastinum. Most frequently it is secondary to trauma, endobronchial or oesophageal procedures, surgery or hollow organ perforation [1]. Spontaneous pneumomediastinum was first described by Hamman in 1939 [2] when no obvious cause is identified. It is more common in youngsters, between the 2nd and the 4th decade, especially in males. Precipitating factors such as cough, labor [3] or drug abuse have been described.
The Macklin effect [4] establishes that alveolar rupture occurs due to increased intrathoracic pressure, which results in air dissecting the bronchovascular sheath until the mediastinum. Thoracic pain, cough and dyspnoea are the clinical signs.

Air may extend to other nearby structures, such as the soft tissues of the head and neck, resulting in subcutaneous emphysema. A crepitus on palpation of the affected body region is a characteristic sign, while neck pain is a rare one.
Rarely, air in the deep cervical tissues of the neck may also reach the spinal canal through the intervertebral foramina [5], causing pneumorachis. Most frequently it is asymptomatic, but signs of spinal cord compression may develop.

The chest radiograph is a good first-line technique in the evaluation of pneumomediastinum and might reveal: continuous diaphragm sign, air outlining the mediastinic structures, pneumopericardium, ring around artery sign or the tubular artery sign. It may also show air in the soft tissues of the chest or neck and the gingko leaf sign if air is seen involving the pectoralis major muscle.
The CT is a more sensitive technique, being able to show small amounts of free air, not visible in the chest radiograph. It also has the advantage of establishing a better anatomy for the mediastinic free air and reveal the presence of lung pathology such as subpleural bullae that might have caused the pneumomediastinum. CT can also reveal the presence of pneumorachis.

Treatment is supportive, with oxygen, sedatives and analgesics being usually sufficient. Recurrence is uncommon and also responds to conservative measures.

Differential Diagnosis List

Final Diagnosis

Spontaneous pneumomediastinum, subcutaneous emphysema and pneumorachis

URL:	https://www.eurorad.org/case/13363
DOI:	10.1594/EURORAD/CASE.13363
ISSN:	1563-4086